In the Fraunhofer diffraction experiment,$L$ is the distance between the screen and the obstacle,$b$ is the size of the obstacle,and $\lambda$ is the wavelength of the incident light. The general condition for the applicability of Fraunhofer diffraction is:

• A
  $\frac{b^2}{L \lambda} \gg 1$
• B
  $\frac{b^2}{L \lambda} = 1$
• C
  $\frac{b^2}{L \lambda} \ll 1$
• D
  $\frac{b^2}{L \lambda} \neq 1$